Rodent Smarts – Why It Pays to Live with Humans

While the idea of rodents living in a house may cause many people to feel a bit uneasy, apparently this relationship serves these little fellows quite well, specifically in the formation of greater intelligence. According to a recent study in the journal Frontiers in Zoology, pet rodents are smarter than their wild counterparts, likely due to living with humans. In the study, domesticated and wild guinea pigs were placed in a water maze, with the domesticated animals ultimately performing better and showing superior problem-solving abilities, likely as a result of having to make previous adaptations to man-made environments. This finding is especially surprising when considering previous research noting that domestication reduced rather than increased the brain sizes of domesticated guinea pigs and other rodents.

Horse Memories: Maybe Mr. Ed Was Onto Something?

Just as some rodents have surprising intelligence, the same can be said about horses, which display amazing long-term memory skills and incredible loyalties. A recent study in the journal Animal Behavior found that horses which had pleasurable experiences (specifically those marked by positive reinforcement) with familiar humans such as their trainers were more likely to remember and display greater affection towards those people after months of separation. Furthermore, such horses were more likely to warm up to and be affectionate with (i.e. sniff and lick) unfamiliar people. According to the study’s researchers, such behavior reveals that horses are able to develop positive memories of humans and hints at the wonderful intelligence of these majestic creatures.

The Bonobo Head Shake: When No Means No

While animals can be extremely friendly and loyal like humans, they can also lay down the law when necessary. Take bonobos as a great example. According to recent research in the journal Primates, adult bonobos were observed for the first time shaking their heads in disapproval of certain behavior by younger bonobos. For example, after a mother bonobo removed a piece of leek from a youngster who was playing with rather than eating the food, the mother began to shake her head at the infant when it went back after the leak, as if she was saying “no” to the behavior. Previously bonobos had only been observed shaking their heads while playing. Now researchers suggest that the bonobo head shake could be a “primitive precursor” to the human head shake expressing negativity.

Mouse Grimaces: Facial Expressions of Pain

Could pain, like the negative headshake, be evolutionary? According to recent research in the journal Nature Methods, this is certainly a possibility, specifically when considering how mice exhibit pain with different facial expressions. In the study, researchers recorded the facial movements of mice after they were injected with a substance causing inflammation. Like humans, the mice showed discomfort through facial expressions, with narrowing eyes, bulging cheeks, moving ears, and bunched-up or flattened-out whiskers indicative of more intense pain. It is important to note that the mice expressions returned to normal following the administration of a pain reliever. From these experiments, the researchers were able to create a sliding mouse grimace scale that will be used in the future to reduce the suffering of mice and other animals during medical research.

Chimpanzee Grieving: Similar Reactions to Death

While it is seemingly certain that animals understand the realities of death, recent research on grieving chimpanzees reveals far more awareness than what had been previously recognized. As detailed in the journal Current Biology, a study examined the reactions of three adult chimpanzees as an elderly chimp was passing away. Sensing the inevitable, the three chimpanzees displayed many different types of grieving behavior: they stayed close to the dying female, gently stroking her hair as if providing comfort; they tossed and turned while sleeping at night, suggesting that they were disturbed by the impending death; they apparently attempted resuscitation to see if the sick chimp was still alive; they slowly moved away from the body when the chimp had died; they later returned to the body for apparently either one last attempt at resuscitation or a final confirmation of death; and they cared for the dead chimp’s body, gently grooming and removing straw from her face. Based on these findings, researchers suggest that it may be more beneficial for the grieving and farewell process to let chimpanzees die in their natural group settings rather than in isolation.